Automatic pipettor

ABSTRACT

Apparatus for automatically and rapidly transferring precise, accurate multiple quantities of samples, such as blood serum, and reagent to the rotatable transfer device of a rotating spectrophotometer analyzer.

United States Patent Shapiro et al. Apr.v2, 1974 [54] AUTOMATIC PIPETTOR 3,679,367 7/1972 Negersmith ct al 23 259 [75] Inventors: Stephen L Shapiro, scarsdale; 3,728,079 4/1973 Moran 23/259 X Thomas Picunko, Bronxville, both of N.Y. Primary ExaminerMorris O. Wolk [73] Ass1gnee: Union Carbide Corporation, New Assistant E S i York, Attorney, Agent, or FirmFredrick J. McCarthy, Jr. 22 Filed: July 17, 1972 [21] App]. No.: 272,492

- [57] ABSTRACT [52] U.S. Cl. 23/253 R, 23/259, 73/425.4 P [51] Int. Cl. ..G01n 33/16, GOln 1/14 I [58] Field of Search 23/259, 253, 292; Apparatus aummatlcany and transfemng 73,14254 P; 141/130 precise, accurate'multiple quantities of samples, such as blood serum, and reagent to the rotatable transfer [56] References Cited device of a rotatingspectrophotometer analyzer.

UNITED STATES PATENTS 3,594,129 7/1971 Jones 23/259 X 3 Claims, 22 Drawing Figures if? I M) I; /llr 2 J 75 '6 33/3 ,d

MENTEB APR 2 i974 sum 01am PATENTED APR 2 1974 sum 02 ur 1'1 ?AIENIEOAPR 2 I974 3.801. 283

SUPPLY 7 Sample Quantity Selector PATENTED APR 2 I974 SHEET DBIIFH PATENTEUAPR 2 I974 sum 07 or n gNg AUTOMATIC PIPETTOR blood serum and other body fluids, food products, and

the like. Since numerous analyses can be performed rapidly and simultaneously, these devices are of particular interest wherein a large number of samples is involved or a variety of tests on one sample is desired.

The device described in Analytical Biochemistry, I

2.8 ,-2 @2192? l s P i p of qv l flsem spectrophotometry wherein absorbancies of a liquid sample and a reference solution are intercompared.

-The system is basically a series of cuvets arranged around the periphery of a rotor so that when it is spun, centrifugal force simultaneously mixes and transfers reagents and samples to the cuvets where an analysis is made spectrophotometrically. A rotatable transfer device is provided which contains rows of cavities arranged concentrically. Samples to be analyzed are placed in one row of cavities and the reagents are placed in the other row of cavities. The transfer device is then indexed and positioned in the rotor as the rotor is accelerated,centrifugal force moves the sample and the reagent to a transfer cavity, where they are mixed and the mixture of reagent and sample is then moved through a communicating passage into the cuvet. The filled cuvets rapidly spin past a fixed light beam, and the transmission of light through the cuvets, i.e., through the reacting solution, is measured.

It is important vin utilizing analyzers of the type described above, that the sample and reagent be introduced to the transfer device rapidly and in accurate amounts in order to ensure accuracy of the tests, to avoid wastage of expensive reagent, andreduce the time required, and hence the expense of testing.-

It is therefore-an object-of the present invention to provide an easily operated apparatus for rapidly transferring accurate multiple quantities of serum and reagent to a rotating spectrophotometer analyzer.

Other objects will be apparent from the following de scription and claims taken in conjunction with the drawings in which FIG. I shows an elevational cross-section of a rotating spectrophotometeranalyzer FIG. Ia shows a plan view of the device of FIG. 1'

FIG. 2 shows an isometric sketch of an assembled and enclosed apparatus in accordance with the present invention FIG. 2a shows a partial plan view of the assembly of FIG. 2 7

FIG. 3 and 3a shows in prespective mechanical components of the apparatus of the present invention involved in transfer of sample and reagent quantities, together with associated electrical connections FIG. 4 shows the manner of assembling certain removable portions of components employed in the apparatus of the present invention 2 FIG. 5a shows the positions taken by certain portions of the apparatus of the present invention during operation involving the transfer ofsample quantities FIG. 5b shows the positions taken by certain portions 5 of the apparatus of the present invention during operation involving the transfer of reagent quantities FIG. 6 is a timing chart correlating the positions illustrated in FIGS. 5a and 5b FIG. 7 illustrates in some detail the pumping mecha-' nism involved in the transfer of samplequantities by the apparatus of the present invention FIG. 8a illustrates cam operation involved in the transfer of sample quantities by the apparatus of the present invention FIG. 8b illustrates cam operation involved in the transfer of reagent quantities by the apparatus of the present invention A FIG. 9 illustrates cam operation involved in the picking up and dispensing of reagent FIG. 10 illustrates the cam operation involved in the actuation of electrical switches which control the dispensing of reagent andwater by the apparatus of the present invention.

FIGS. 11a and 11b illustrate valve porting for reagent pick-up and dispensing by the apparatus of the-present invention FIGS. 12a and 12b illustrate valve porting for water pick-up and dispensing by the apparatus of the present I invention Y I FIG. 13 shows a magnetic switch configuration employed in the apparatus of the present invention FIG. 14 is a schematic further illustrating the electrical operation involved in the apparatus of the present invention i in the operation of the apparatus of the present invention.

With reference to the drawing, FIG. 1 and lain particular, and the rotating spectrophotometeranalyzer shown therein, there is illustrated a rotatable loading disc 1 (hereinafter referred to as atransfer disc) suit ably made of Teflon* (fTrademark of E. I. duPont deNemours) which comprises a plurality of cavity locations 3 with .each location havinga sample cavity 5 and reagent cavity 7. A slot to enable indexing of the transfer disc I, by way of pin 10, is shown at 9. Operating procedure involves the placing of reagent in the cavities 7 and sample in the cavities 5. With the loaded transfer disc 1 indexed and positioned in rotor assembly 11, each row of cavities, i.e. each cavity location 3, is aligned with a respective cuvet l2 and as the rotor assembly 11 is driven, centrifugal force moves the con,- tents of the sample and reagents to the outermost transfer cavities 13. Sample and reagents are mixed and transferred from cavity 13 through'channels 15 to their respective cuvets 12. The filled cuvets l2 rotate be tween light source 17 and photomultiplier detector 19. The signals provided by the photomultiplier detector 19 indicate any light transmission changes due to reaction between reagent and sample.

The general operation of the apparatus of the present invention, which is to provide a fully loaded transfer disc 1, for use in an analyzer of the type mentioned and described above, can be described with reference to FIGS. 2 and 2a. In FIG. 2, transfer disc I is rotatably mounted in assembly 20, as is a sample ring 30. Trans fer disc 1 and sample ring 30 are indexed and held to- FIG. 15 illustrates the indexing mechanism involved I gether as hereinafter more fully described. Sample cups 32 are placed in equally spaced apertures on the sample ring 30 as indicated and contain the sample of inter est e.g. blood serum. Upon pressing'power button 34, electrical energy is applied to the unit and upon pressing cycle button 36, operation is commenced whereby sample, reagent and diluent are delivered sequentially to the desired'cavity locations 3 in the transfer disc 1 through the corrdinated action of probe supporting sample diluent arm 40 and probe supporting reagent arm 42, in conjunction with other components as here-' inafter more fully described. Sample is'delivered from cups 32, reagent from reagent reservoir 43 and diluent from diluent reservoir 46.

The present invention will be more fully understood by reference to FIGS. 3 and 3a wherein a probe supporting sample/diluent arm 40, and a probe'supporting reagent arm 42 are shown engaged via cam 44 and shaft 45 to drive motor 48. Shaft 45 is rotatably supported by frame members 902 and 903. Probes 87, 118 and 132 are all initially radially aligned with the sample cup 32 and indexed in the first position indicated at aa in FIG. 3. In this indexed position, switch 140 is held closed by extension 93 of actuating arm 91 for reasons hereinafter described. The indexing of the apparatus is hereinafter specifically described in connection with FIG. 15. Cam 44 comprises two sections 440 and 44b, fixedly mounted on shaft 45, which are configured as illustrated in FIGS. 8a and 8b to provide the sequential motion illustrated for the sample/diluent arm 40 and reagent arm 42 in FIGS. 5a and 5b and correlated in the timing chart of FIG. 6. The configuration for cam section 44a, controlling the sample/diluent arm 40, is shown in FIG. 8a, while that for section 44b, controlling reagent arm 42 is shown in FIG. 819. As illustrated in FIG. 3 and also in FIG. 8a, the control of sample/diluent arm 40 is provided by pivoted vertical support member 50, pivoted cam following member 51 and pivoted horizontal transfer member 52. Members 51 and S2 engage cam section 44a by way of cam followers 54 and 56 respectively. Cam follower 56 is engaged in groove 57. Reagent arm 42 is similarly cooperatively engaged with cam section 44b by way of members 58,59 and 60 and cam'followers 62 and 64. Cam follower 62 is engaged with groove 61 as more clearly illustrated in FIG. 8b. As can also be seen from FIGS. 3 and 3a, drive shaft 45 is fixedly coupled to reagent- 37, shown in FIG. 3, which provides conventional direct current voltages employed in the operation of various switches, relays-and related devices as hereinafter more fully described. Upon subsequent energization of cycle button switch 36, to place the apparatus of the present invention in operation, cycle light 39'is turned on, illuminating cycle button 36 and energizing relay 41 via line 905, single pole double throw switch 140, and line 906 In the initial indexed position switch 140 is actuated due to extension 93 of arm 91. Relay 41 is connected'in a well known manner such that it remains energized after cycle button switch36 is released; i.e. relay 41 is latch up connected. With relay'41 energized, electrical power is applied via connector 43, from motor driver unit 45 (described more fully hereinbelow in connection with FIG. 14), to a conventional stepping motor 72 which is engaged to the sample/diluent pump assembly 74. Sample/diluent pump assembly 74 is illustrated in detail in FIG. 7 and comprises a micrometer 76 coupled to the shaft of the-stepping motor 72; a plunger 78 engaged to micrometer shaft 80; and a syringe barrel 82, which together with connector chamber assembly 84 encloses plunger 78. Spring 85 holds plunger 78 in contact with micrometer shaft 80 via conventional ball thrust 79, and connector chamber assembly '84 is fixed by conventional ball plunger arrangement 89 within outer housing 86 whereby syringe barrel 82 moves up or down depending on the direction of rotation of stepping motor shaft 75 With particular reference to FIGS. 3 and 5a and 5b, when the cycle buttom switch 36 is actuated as above indicated, stepping motor 72 drives syringe barrel 82 upward causing diluent to be taken up from diluent reservoir 46 by way of probe 87, suitably made of polypropylene, and supported on'sample/diluent arm 40, and tube 88. At this time, the sample/diluent arm 40 is at the First Position shown in FIG. 5a with probe 87 immersed in diluent in reservoir 46 as illustrated. Sample/diluent arm 40 and probe 87 remain in th First Position until actuating arm 90 (fixedly engaged to connector chamber assembly 84) contacts arm of switch 92 and causes single pole double throw 92 to close. The closing of switch 92 energized relay 47 via lines 907 and 908 which stops stepping motor 72, as hereinafter described in connectionwith FIG. 14, and causes latch up connected relay 94 to be energized whereby power is applied from connector 1700 via line 909 to drive motor 48 which commences its rotation at usual arrangement is for ring 30 to support 30 sample cups'arid 5S microliters of diluent" are provided for each sample. Under these circumstances actuation of switch 92 byarm 90 would not occur until at least 1.65 milliliters of diluent were picked up.

Movement of sample/diluent arm 40 toward transfer disc 1 commences a small time increment after the actuation of switch 92, controlled by cam section 44a, from the probe dwell position 97 indicated in FIG. 8a, which corresponds to the First Position of FIG. 50. Transfer disc 1 is initially positioned, i.e. indexed so that the sample cup 32 in the first loading position is radially aligned with probes 87, 1 18 and 132 as indicated at a'a in FIG. 3 and elsewhere. As shown more clearly in FIG. 15, transfer disc 1 is supported by turntable 600 and engaged by spindle 605 and pin 610, which engages slot 9. Sample ring 30 is similarly engaged by pin 610 and supported by turntable 600, an aperture 615 being provided in the base of sample ring 30 instead of a slot. When arranged as described, sample cups 32, mounted in openings 620, will be radially aligned with opposite sample cavity 5 and reagent cavity 7 and the other cups and cavities will also be aligned with the probes supported by arms 40 and 42 during their respective loading cycles. Supporting spindle shaft 605 of turntable 600 is rotatably mounted in base shaft 625 which is fixedly positioned with respect to drive motor 48. Conventional ratchet pawl assembly 114 is fixedly coupled by arm 630 to spindle shaft 605 and maintains the radial alignment of sample cups, reagent and sample cavities and probes throughout the loading cycle for each indexed position. Upon actuation of push pull rod 112 by slidably engaged eccentric 70, at the end of a loading cycle, as hereinafter described, arm 630 is raised to release pin 635 from the engaging opening 640, and move to the right to engage advanced opening 645 whereupon eccentric 70 continuing to act through push rod 112, rotates turntable 600, sample ring 30 and transfer disc 1 to the left as shown so that another sample cup 32, and its associated reagent cavity 7 and sample cavity 5, are in radial alignment with the probes supported by arms 40 and 42.

With drive motor 48 actuated and continuously rotating as previously described, cam section 44a turns and the sample/diluent arm 40 moves to the Second Positionshown in FIG. 5a corresponding to the cam location shown at probe dwell position 57 in FIG. 8a due to the coaction of cam contours 206 and 207 shown in FIG. 8a. In this position, with probe 87 immerscd in the sample cup 32, switch 102 is actuated by foot actuator 47, fixedly attached to pivoted arm support member 50. Actuation of switch 102 causes rotation of stepping motor 72 in the same direction as its initial rotation by appropriate connection of lines 3000 and 4000 to grounded line 5000, as described more fully in connection with FIG. 14, thus drawing sample into pump assembly 74. By prior adjustment of thumbwheel switch 108, as also hereinafter described in connection with FIG. 14, stepping motor 72 is caused to stop after a predetermined number of steps, which corresponds to a particular predetermined amount of sample, e.g. from 1 to 50 microliters usually about 20 microliters. Sample probe 87, suitably made of polypropylene, is large enough so that it contains the entire sample picked up and sample does not enter tube 88.

The sample/diluent arm is subsequently moved .to the Third Position shown in FIG. 5a due'to the coaction of cam contours indicated at 106 and 107 in FIG. 8a. The Third Position of FIG. 5a corresponds to probe dwell location 300 shown in FIG. 8a. Switch 102, which was released when the sample/diluent arm 40 moved from the Second Position of FIG. 5a, is reactuated in the Third Position of FIG. 5a by foot actuator 47. This causes stepping motor 72 to be reactuated and rotate in a direction opposite to-its initial rotation whereby glass barrel 82 moves down and dispenses a predetermined amount of the contained sample and diluent, e.g., a total of about to 99 microliters, usually about 70 microliters, via probe 87 into aligned sample cavity 5. The amount of sample diluent dispensed into serum cavity 5 is controlled by a second thumbwheel switch 104 which stops stepping motor 72 after a predetermined number of steps as hereinafter described in connection with FIG. 14. Diluent, e.g. distilled water, is used as the sample carrier and avoids retention of sample in the probe 87 by washing out the probe with each dispensing of sample.

The sample/diluent arm 40 with probe 87 is moved back, i.e. returned to the First Position illustrated in FIG. 5a which corresponds to the probe dwell location shown at 97, due to the coaction of cam contours 306 and 307 shown in FIG. 8a. In this position the sample probe 87 is rinsed on its'exteriorin the diluent in diluent reservoir 46. Switch 110 is actuated by sample/diluent arm 40 upon its return to its First Position (FIG. 5a) and counting circuitry is re-set by way of line 1800 as hereinafter described in connection with FIG. 14. Just prior to the return of sample/dilunt arm 40 to the First Position, (FIG. 5a) eccentric member starts to move push-pull rod 112 which causes ratchet pawl 114 to rotate turntable 600 and advance the next sample cup 32 opposite the sample/diluent arm 40 in the manner previously described.

With reference to the previous discussion, and FIGS. 3 and 3a when the drive motor 48 was started .and placed in continuous rotation by contact of actuating arm of the sample/diluent pump assembly 74 with switch 92 (when the sample/diluent pump 74 was adequately filled with diluent), reagent arm 42 and probes 118 and 132 were in the First Position shown in FIG. 5b, corresponding to probe dwell location 116 as shown in FIG. 8b. In this position reagent probe 118 is immersed in reagent contained in reagent reservoir 43. Reagent probe 118 communicates via tube 120, a three-way solenoid reagent valve 122, and tube 123 to reagent syringe 124 held by clamp 125 to mounting block 126 fixedly secured to base member 129. Water syringe 127 is similarly mounted and communicates via tube 155, three-way solenoid water valve 128, and tube 130 to water probe 132.

While reagent arm 42 is in the First Position shown in FIG. 5b, reagent/water cam 66, acting with spring 133,- through follower 135, shaft 136, and plunger holder 138', moves the plunger 134 of reagent syringe 124 to the right thus drawing reagent into probe 118. Probe 118 is suitably detachable from tube 120 and thus can be readily replaced when a different reagent is to be used. Since reagent never travels beyond the probe 118 no purging of tube 120 or syringe 124 is required upon change of reagent. Reagent syringe 124 contains air, initially about 70 microliters, and reagent never enters the syringe 124 but is retained in the probe 118. The reagent volume drawn into probe 118 is controlled byeither switch 141 or switch 142, the selection of switch 141 or 142 is determined by panelvolume selector switch 144 located on assembly 20 as shown in FIG.' 2. A DC voltage is provided via line 911 to switch 144 from power supply 37 with the contacts of relay 143 in the position indicated. By selecting switch 141 (Vi) a relatively small volume of reagent, such as 250 microliters, can be provided in reagent probe 118 via three-way reagent solenoid valve 122 which as controlled by switch 141. By selecting switch 142 is a larger volume of reagent, such as 350 microliters, can be provided in reagent probe 118 via three-way solenoid reagent valve 122, which is controlled by switch 142. A solenoid valve 122 receives an actuating DC. voltage via line 912 from either switch 141 or 142 by way of line 913 or 914.

The selection of either switch 141 or switch 142 is controlled by volume selector 144 which is manually positioned prior to actuation of cycle button 36, to call for the pick-up of either a relatively large or relatively small quantity of reagent depending on the particular test involved, e.g. either 350 microliters or 250 microliters. For the larger amount, i.e. 350 microliters, switch 144 is positioned to energize switch 142 by way of relay 143. Thus with reagent arm 42 in the First Position", illustrated in FIG. Sb corresponding to probe dwell location l16 in FIG. 8b, 'microswitch cam 68 is positioned with respect to switch 142 as illustrated in FIG. 10, at the beginning of the First Position (FIG. Sb) and switch 142. is actuated when point 200 of microswitch cam 68 contacts arm 202 of switch 142. Actuation of switch 142 causes an actuating electrical signal to be applied via lines 912 and 914 to reagent solenoid valve 122 opening port 121 to reagent probe 118 via tube 120 and to reagent syringe 124 via tube 123 as shown in FIG. 11b. Reagent solenoid valve 122 remains in this condition until microswitch cam 68 is rotated to until rotation of reagent/water cam 66 to location 225 whereupon it is moved to the right to pick up 100 microliters of reagent from reservoir 43 by way of reagent probe 118. After the "dwell period indicated at 227 plunger 134 moves again to the right'to draw an additional 250 microliters of reagent into reagent probe 118 at location 229 in FIG. '9. Reagent probe 118 is large enough so that the entire amount of the reagent pickedup is contained in the probe 118. Plunger 134 then remains stationary during rotation of reagent/water cam 66 through location 231 during which period reagent'arm 42 moves to the Second Position shown in FIG. b and corresponding to the probe dwell location 130 in FIG. 8b due to the coaction of cam contours 406 and 40'? illustrated in FIG. 8b. At location233 indicated in FIG. 9 the plunger 134 is moved'to the left and dispenses the reagent in probe 118 into the directly underlying reagent cavity 7. The dispensing of all the reagent in probe 118 into reagent cavity 7is ensured for the subsequent cycles by the drawing of an incremental volume of air into reagent syringe 124 by the rightward movement of plunger 134 during rotation of water/reagent cam 66 through the location 235. During this period, reagent arm 42 is returning to the First Position shown in FIG! 5b corresponding to probe dwell location 116 in FIG. 811 due to the coaction of cam contours 506 and 507 in FIG. 8b. The air picked up in reagent syringe 124 as described above, (plunger 134 travel equivalent to about 70 microliters of reagent) together with the air initially present in reagent syringe 124 forces all of the reagent, i.e. 350 microliters, from reagent probe 118 when reagent/water cam 66 travels through location 233 which causes a plunger travel cor-.

responding to about 420 microliters of reagent.

When switch 141 is selected, by the positioning of switch 144, instead of switch 142, reagent solenoid valve 122 is not energized to the position of FIG. 11 until point 245 of microswitch cam 68 contacts arm 247 of switch 141 as indicated in FIG. 10. At this time an actuating DC. voltage from switch 144 is applied to solenoid valve 122 via lines 913 and 912. This corresponds to location 227 in FIG. 9 illustrating the operation of reagent/water cam 66 and syringe plunger 134. Thus only 250 microliters of reagent are drawn into reagent probe 1 18; all other operations of reagent syringe 124 remain the same however.

7, upon the completion of one revolution of drive shaft 45, the reagent arm 42 is moved back to the First Position shown in FIG. 5b which corresponds to the cam location shown at 116 in FIG. 8b, with both the sample/diluent arm 40 and the reagent arm 42 returned, the apparatus is in position to repeat the aforedescribed sample and reagent loading operation for all the remaining sample cup positions. The foregoing operating sequence is exemplified in the time diagram of FIG. 6. When the above described operation is being completed for the last cup position in sample ring 30, actuator 91, attached to shaft 605, has moved completely around and actuates switch by way of extension 93 and relays 41 and 94 arede-energized. Power remains applied to the drive motor 48 on lines 909 and 910 via switch 140 and switch 110. When switch 110 is actuated by sample/diluent arm 40, due to the return of the sample arm 40 to its First Position (FIG. 5a), following the actuation of switch 140, power to drive motor 48 will be interrupted, and the cycle is completed. For 30 samples, this can readily be accomplished in about 3% minutes or less.

Under some circumstances, all the sample cup positions on the sample ring 30 will not be used. In such a case, with reference to FIG. 13 amagnetic plug 147 is placed in the sample cup hole immediatelytollowing the last sample containing cup as indicated. This may or may not be the final cupposition. Magnetic plug 147 conveniently comprises a magnet 701 imbedded in a suitable material such'as. Teflon.

Upon alignment of magnetic plug 147 with probes 87, 118 and 132, the underlying magnetic switch suitably mounted on support 146, is actuated which energizes relay 143 via lines 915 and 916 by way of the alternating current voltage applied to the drive motor 48. Relay 143 is latch up" connected so that it remains energized when magnetic switch 145 is released. When no voltage is being applied to drive motor 48 relay 143 is always de-energized. With relay 143 energized, due to the positioning of magnetic plug 147 above magnetic switch 145, a DC. energizing electrical signal is applied to switch 149 via line 920 and removed from either 142 or 14l,whichever had been previously selected, and with'lever 247 of switch 149 actuated by point 255 of microswitch cam 68, with reference to FIG. 10, a signal isapplied to water'solenoid valve 128 via connector 917, indicated in FIG. 3a to position the valve as illustrated in FIG. 12b. As shown in FIG. 12b, water can now pass from syringe 127 via tube through valve 128, tube 130 to water probe 132. The motion of plunger 159 of water syringe 127 corresponds to that of reagent syringe 127 corresponds to that of reagent syringe 124, thus during the rotation of water/reagent cam 66, through location 233, with reference-to FIG. 9, water is dispensed via water probe 132 (suitably of stainless steel) into reagent cavity 7. However, reagent will not be dispensed under these circumstances, since the removal of the D.C. electrical signal from switch 142 or 141 caused reagent solenoid valve 122 to be de-energized, as illustrated in FIG. 11a. Under these conditions, conduit 1000 is exposed to air and reagent is neither picked up nor dispensed.

Prior to the actuation of magnetic switch 145, with solenoid water valve 128 de-energizedas indicated in FIG. 12a, water was drawn into water syringe 127 from receptacle 151 via tube 153 during the rotation of water/reagent cam 66 through locations 225 and 229 and 235 indicated in FIG. 9 and returned from water syringe 127 to receptacle 151 via tube 153 during rotation of cam 66 through location 233. However, with water solenoid valve 128 controlled by switch 149, as described above, water, (which is continuously present in water syringe 127) instead of reagent is dispensed into reagent cavity 7 of transfer disc 1 for the position opposite the magnetic plug 145 and all following positions until the completion of one revolution of transfer disc 1. This feature conserves reagent, which is quite expensive, since reagent is loaded only into the cavities which also hold samples.

As a practical matter, magnetic plug 145 is usually used, at least in the last cup position, to provide a water reference" for use when the loaded transfer disc is subsequently used with a spectrophotometer analyzer as illustrated in FIG. 1.

With reference to FIG. 14, an oscillator 900, gate circuits 920 and 922, encoder 925, driver circuit 935 and counters 940 and 945 are shown comprising Motor Driver Unit 45 illustrated schematically in FIG. 3. Counter 940 can be a conventional decade counter and counter 945 can be a conventional binary counter. Associated with Motor Driver Unit 45 are Thumbwheel type hand settable switches 104 and 108, and stepping motor 72. Switches 104 and 108 are suitably commercially available binary coded decimal Thumbwheel switches. All of the foregoing can be commercially available, conventional components; With a sample ring 30 and a transfer disc 1 indexed in its initial posi tion as previously described in connection with FIG. 3, switch 140 is actuated by extension 93 of arm 91. Switch 110 is actuated in the open position due to contact with member 399 which is fixedly engaged by way of arm 52 with sample/diluent arm 40, which is in the First Position (FIG. a). Thus counters 940 and 945 are set to a zero condition by-the ungrounding of connector'1800. Switch 110 is mounted in a fixed position, eg on a suitable extension of frame member 902 (not shown for purposes of clarity). Switch 102 (single pole double throw) at this time is in its initial normally closed position. Stepping motor 72 is immobile at this time since gate circuits 920 and 922 are inhibited due to the state of the signals applied at connectors 1810, 1820, 1830 and 1840. When cycle button switch is actuated (after Power switch 34 is closed energizing Power Supply 37 and hence oscillator 900) relay 41 is energized through the closed switch 140 and pulses 910 from oscillator 900 are applied to stepping motor 72 via gate circuit 922 due to the grounding of connector 1810, which open gate circuit 922. Pulses as indicated at 910 are applied through gate circuit 922 to encoder 925 which converts the pulses 910 to the conventional form 930 required by stepping motor 72. The signals from conventional driver circuit 935, which translates the applied voltage levels to a higher level, are applied to stepping motor 72 which rotates and causes diluent to be taken up by sample/diluent pump 74. When switch 92 (illustrated in FIG. 3) is actuated upon filling of sample/diluent pump 74, relay 47 is energized via line 907 opening line 1810 thereby inhibiting gate circuit 922 and stepping motor 72 is stopped. Relay 94 is energized when switch 92 is actuated causing drive motor 48 to be energized via connector 5000 as indicated in FIG. 3 to rotate and move sample/diluent arm 40 to the Second Position thereby closing and i0 grounding switch 110. This changes the signals to counters 940 and 945 which are placed in condition to count when switch 102 is next actuated, i.e. when sample/diluent arm 40 reaches the Second Position (FIG. 5a) with probe 87 in the sample cup 32. This actuation of switch 102 interrupts the grounded connection at 3000 to direction counter 945 and re-applies the grounded connection via connector 4000. Direction counter 945 can be a conventional by 2 binary counter which provides a change of state upon a second change in input signal level. The foregoing operation ungrounds the connection 8000 to counter 940 and thereby open gate circuit 920 whereby pulses from oscillator 9000 are applied to stepping motor 72, and stepping motor 72 is reactuated in the same direction, to pick up the required amount of sample as set by switch 104. The oscillator pulses are counted by counter 940 and compared with the pre-set value in thumbwheel switch 104. When the desired number of pulses is counted, corresponding to a desired sample volume the stepping motor 72 is stopped by a signal v over line 1840 which inhibits gate circuit 920.

As sample/diluent arm 40 move to the Third Position indicated in FIG. 5a switch 102 is released interrupting the grounded connection at 4000 and returning the grounded connection at 3000 to direction counter 945 and counter 940. The signal now applied via'connector 8000 re-sets counter 940 and the polarity of the signals from encoder 925 will be reversed when sample/diluent arm 40 reaches. the Third Position. Gate 920 is opened via connector 1820 and switch 102 is again actuated, and stepping motor 72 is-actuated and rotates in the opposite direction to dispense sample diluent. The pulses from the oscillator 900 are now counted by counter 940 and compared with the value set in thumbwheel switch 108 via connector 965. When the pre-set number of pulses has been counted, corresponding to the desired volume of sample diluent, stepping motor 72 is stopped by the inhibiting of gate circuit 920 due to the signal applied via connector 9000. Upon return of sample/diluent arm 40 to,the First Position indicated in FlG. 5a switch 110 is opened and ungrounded and counters 940 and 945 are reset to their initial zero or starting position.

At this time the turn table 600 moves tothe next position and switch is released and relays 41 and 94 are de-energized and power to drive motor 48 is applied now through switch 140 and switch 111 via connectors 1700 and 909. For the drive motor 48 to be tumed off at the end of one complete revolution of transfer disc 1 both switch 110 and 111 will have to be actuated i.e. opened, which will occur when arm 91 returns to its initial position. When transfer disc 1 is advanced to the next and each subsequent sample cup position, as previously described in connection with FIG. 4, all of the foregoing operations occurs, except that gate circuit 922 remains inhibited thus preventing the pick-up of additional diluent by preventing operation of stepping motor 72 when sample/diluent arm 40 is in the First Position (FIG. 5a). This is accomplished by the deenergization of relay 41 and the ungrounding of connector 1810 upon the release of switch 140 by movement of turntable 600 to the next or second filling position. Connector 1810 remains ungrounded, and gate circuit 922 remains inhibited for all loading positions after the initial loading position.

We claim:

1. Apparatus for delivering multiple, discrete quantiity and a sample cavity, said apparatus comprising ro- 7 upon electrical actuation of said drive means, said shaft means being positioned such that the axis of rotation thereof is substantially perpendicular to the axis of rotation of said rotatable support means; first, second and third cam means engaged to said shaft'means whereby continuous rotationalmotion is imparted thereto upon actuation of said drive means; diluent vessel means adapted to contain liquid diluent arranged adjacent said annular means; reagent vessel means adapted to contain liquid reagent arranged adjacent said annular means; afirst arm member cooperatively engaged to said first cam member; a first probe member adapted to contain liquid supportably engaged to said first arm member,flsaid first probe member being continually moveable upon cooperative movement of. the first cam member and first arm member from an initial first dwell position. immersed in diluent in said diluent vessel means, thence to a second dwell position immersed in sample in a receptacle of said annular member, thence to a third dwell position above the sample cavity of said transfer disc and thence'back to said first dwell position;-a second arm member cooperatively engaged to said second' cam member; a second probe. member adapted to contain liquid supportably engaged to said second arm member, said second probe member being continually moveable upon cooperative movement of said second cam member and said second arm memberfrom an initial first dwell position, immersed in reagent in said reagent vessel means; thence to a second dwell position above the reagent cavity of said transfer disc, and thence back to said first dwell position; means engaging said rotatable means and said shaft means to initially substantially align a selected receptacle of said annular means with said first and second probe members along a radius of said transfer disc and to similarly align another receptacle upon each return of said probe members to their respective first dwell positions; first electrical control means adapted to be actuated whenever said selected receptacle of said annular member is initially positioned; a first pump means communicating with said first probe means having reciprocally moveable means to enable intake and dispensing of liquid through said first probe member; electrically operable stepping motor means engaged to said reciprocally moveable means of said first pump means adapted to be actuated only during actuation of said first electrical control means and to rotate in an initial direction to cause diluent to be drawn from said diluent vessel means when said first probe member is in its initial first dwell position; second electrical control means adapted to be actuated upon the drawing of a predetermined quantity of'diluent from said diluent vessel means to stop rotation of said stepping motor means and actuate said drive means; third electrical control means adapted to be actuated when said first probe member is "in its second dwell position to cause said stepping motor means to rotate again in its initial direction of rotation and cause said first pump means to draw sample into said firstprobe member from said sample vessel means and to be actuated when said first probe member is in its third dwell position to cause said stepping motor means to rotate in a direction opposite to its initial direction of rotation to cause said first pump means to dispense sample through said first probe member;

' fourth electrical control means adapted to stop said stepping motor means whenever. a predetermined amount of sample is drawn into said first probe member by said first pump means; fifth electrical control means adapted to stop said stepping motor means whenever a predetermined amount of sample plus diluent is dispensed through said first probe member by said first pump means; second pump means communicating with said second probe member cooperatively engaged to said third cam means to cause a predetermined quantity of reagent to be drawn into said second probe member whenever said second probe member is in its first dwell position and to cause dispensing of said predetermined amount of reagent from said second probe member whenever said second probe member is in its second dwell position. v

2. Apparatus'in accordance with claim I additionally comprising a fourth cammember engaged to said shaft means whereby rotational motion is imparted thereto upon actuation of said drive means; sixth electrical control means arranged adjacent said fourth cam member and adapted to' be actuated thereby for a predetermined interval and transmit an electrical control signal for such interval whenever said second probe member is in its first dwell position and while an electrical control signal is applied thereto; seventh electrical control means arranged adjacent said fourth cam member and adapted to be actuated thereby for a predetermined interval different in duration than said first mentioned predetermined interval and transmit an electrical control signal for such interval whenever said second probe member is in its first dwell position and while an electrical control signal is applied thereto; first electrically operable valve means in communication between said second probe member and said second pump means being electrically connected to said sixth and seventh electrical control means and being adapted to be opened upon application of said electrical control signal thereto, and means for selectively applying an electrical control signal alternately to said sixth and seventh electrical control means.

3. Apparatus in accordance with claim 2 additionally comprising a magnetically operable electrical control means arranged adjacent said annular member and substantially in alignment with said first and second probe members; magnet means arranged in a receptacle of said annular member adapted to actuate said magnetically operable switch when substantially in alignment therewith; third probe member adapted to contain liquid supportably engaged by said second arm member being continually moveable in the same man ner as said second probe member; a vessel adapted to contain a reference liquid; third pump means commu nicating with said reference liquid vessel cooperatively engaged to said third cam means to cause reference liquid to be drawn into said third pump means whenever said second probe member is in its first dwell position and to be dispensed from said third pump means whenever said second probe member is in its second dwell position; eighth electrical control means arranged adjacent said fourth cam member and adapted to be -actuated thereby for a predetermined interval and transmit an electrical control signal for such interval whenever said second probe member is in its second dwell position and while'an electrical signal is applied thereto; second electrically operable valve means in communication with said third probe member, said third pump means and said reference liquid vessel being electrically connected to said eighth electrical control means and being adapted to provide communication between said third pump means and said third probe member upon application of said electrical control signal thereto; ninth electrical control means adapted to be actuated upon actuation of said magnetically operable electrical control means to remove any control signal applied to said first electrically operable valve means and apply a corresponding electrical control signal to second valve means. 

2. Apparatus in accordance with claim 1 additionally comprising a fourth cam member engaged to said shaft means whereby rotational motion is imparted thereto upon actuation of said drive means; sixth electrical control means arranged adjacent said fourth cam member and adapted to be actuated thereby for a predetermined interval and transmit an electrical control signal for such interval whenever said second probe member is in its first dwell position and while an electrical control signal is applied thereto; seventh electrical control means arranged adjacent said fourth cam member and adapted to be actuated thereby for a predetermined interval different in duration than said first mentioned predetermined interval and transmit an electrical control signal for such interval whenever said second probe member is in its first dwell position and while an electrical control signal is applied thereto; first electrically operable valve means in communication between said second probe member and said second pump means being electrically connected to said sixth and seventh electrical control means and being adapted to be opened upon application of said electrical control signal thereto, and means for selectively applying an electrical control signal alternately to said sixth and seventh electrical control means.
 3. Apparatus in accordance with claim 2 additionally comprising a magnetically operable electrical control means arranged adjacent said annular member and substantially in alignment with said first and second probe members; magnet means arranged in a receptacle of said annular member adapted to actuate said magnetically operable switch when substantially in alignment therewith; third probe member adapted to contain liquid supportably engaged by said second arm member being continually moveable in the same manner as said second probe member; a vessel adapted to contain a reference liquid; third pump means communicating with said reference liquid vessel cooperatively engaged to said third cam means to cause reference liquid to be drawn into said third pump means whenever said second probe member is in its first dwell position and to be dispensed from said third pump means whenever said second probe member is in its second dwell position; eighth electrical control means arranged adjacent said fourth cam member and adapted to be actuated thereby for a predetermined interval and transmit an electrical control signal for such interval whenever said second probe member is in its second dwell position and while an electrical signal is applied thereto; second electrically operable valve means in communication with said third probe member, said third pump means and said reference liquid vessel being electrically connected to said eighth electrical control means and being adapted to provide communication between said third pump means and said third probe member upon application of said electrical control signal thereto; ninth electrical control means adapted to be actuated upon actuation of said magnetically operable electrical control means to remove any control signal applied to said first electrically operable valve means and apply a corresponding electrical control signal to second valve means. 